Steel wool, chicken wire, fire... urban exploration is being taken to the next level of extreme. Seems nowadays kids aren't content with merely trespassing and snapping some photos... now they're running through abandoned subway tracks twirling these homemade concoctions around while they burn. The result is pretty cool though. Here are a few photos by Pro-Zak, who calls the process "burning," taken in Manhattan, Queens, Brooklyn and even New Jersey.